Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$56.97	13.563%	$64.6968	$64.70	$64.70	$64.70
Purchase #2	$168.56	9.855%	$185.1716	$185.17	$185.15	$185.20
Purchase #3	$68.82	4.205%	$71.7139	$71.71	$71.70	$71.70
Purchase #4	$92.25	10.539%	$101.9722	$101.97	$101.95	$102.00
Purchase #5	$84.96	6.111%	$90.1519	$90.15	$90.15	$90.20
Purchase #6	$126.47	3.699%	$131.1481	$131.15	$131.15	$131.10
Purchase #7	$52.97	4.451%	$55.3277	$55.33	$55.35	$55.30
7 purchase totals =	$651.00		$700.1822	$700.18	$700.15	$700.20